1. Technical Field
Embodiments of the present disclosure relate generally to lithography processes and a method of manufacturing semiconductor devices. Additionally, the embodiments relate to lithography processes utilizing extreme ultraviolet (EUV) rays and methods of manufacturing semiconductor devices using the same.
2. Related Art
As critical dimensions (CDs) and/or pitch sizes of patterns constituting integrated circuits of semiconductor devices become reduced, an extreme ultraviolet (EUV) ray has been considered for source lights which may be used to transfer pattern images of photo masks (e.g., photo reticles) onto wafers during lithography processes. The extreme ultraviolet (EUV) ray has a short wave length of about 13.6 nanometers (nm). Thus, a lithography apparatus using the extreme ultraviolet (EUV) ray may include a mirror optical system and may adopt mirror masks or mirror reticles to perform the lithography process. The mirror masks (or the mirror reticles) may include a mask substrate and mirror layer patterns and absorption layer patterns formed on the mask substrate. The mirror layer patterns and absorption layer patterns may be formed using layout data.
When the EUV lithography processes employing the mirror optical system are performed, the critical dimension (CD) uniformity of the patterns formed on the wafers may be degraded at the edges of field regions which are exposed by the mirror optical system. Specifically, the mirror mask may include at least one field region including image patterns which should be transferred onto a wafer and a black region surrounding the at least one field region. Ideally, the black region should not reflect the EUV rays even though a portion of the EUV rays are irradiated on the black region. Thus, the black region of the mirror mask may be coated with a light absorption layer. However, the light absorption layer may not completely absorb the EUV rays which are irradiated thereon. That is, the light absorption layer in the black region may actually reflect a small portion of the EUV rays. Therefore, the small portion of the EUV rays may be reflected from a surface of the black region to undesirably travel toward other field regions of the wafer, which have already been exposed or are not yet exposed. Accordingly, each of the field regions (particularly, edges of each of the field regions) on the wafer may be exposed at least twice to cause non-uniform CDs of the patterns formed on the wafer. This phenomenon may be referred to as a black border effect. The black border effect may cause degradation of the CD uniformity of the patterns.